Association between sugar and starch intakes and type 2 diabetes risk in middle-aged adults: the Japan Public Health Center-based Prospective Study

Background and objectives: Evidence on the relationship between sugar (mono- and disaccharides) and starch intake and type 2 diabetes (T2D) risk in Asian populations is currently insufficient. We aimed to investigate the association between sugar or starch intake and T2D risk in middle-aged Japanese adults. Methods: Participants comprised 27,797 men and 36,880 women aged 45-75 y with no history of diabetes and critical illness before the survey in 1995-1999 in the Japan Public Health Center-based Prospective Study. We calculated the intake (% energy/d) of sugar (total sugar, total fructose, and each sugar subtype) and starch using a validated 147-item food frequency questionnaire. T2D onset during the five-year follow-up period was defined by self-report, the validity of which was confirmed. ORs and their 95% CIs, adjusted for age, area, family history of diabetes, history of hypertension, occupation, physical activity, smoking and alcohol status, dietary habits, number of birth (for women), and body mass index were estimated using multiple logistic regression with categorical and cubic spline models. The lowest quartile and its median intake were used as reference. Results: During the follow-up, 690 men and 500 women were identified as new T2D cases. In women, the quartiles of total sugar or total fructose intakes were not significantly associated with T2D risk; however, the spline curves showed an increased T2D risk at extremely high intake levels (ORs [95% CI]: 1.88 [1.07-3.31] at 30% energy/d for total sugar and 1.87 [1.103.16] at 14% energy/d for total fructose). Starch intake was positively associated with T2D risk among women in the categorical and spline models (ORs [95% CI] from the spline model: 1.55 [1.13-2.12] at 50% energy/d). In men, sugar and starch intakes were not associated with T2D risk. Conclusions: In this large-scale population-based cohort study, starch intake was associated with an increased T2D risk in women. For extremely high intake of total sugar or total fructose, a possible increased risk cannot be disregarded in women.